Thermoplastic film, microporous film, and laminates thereof, are made at high speeds on the order of about 500 fpm to about 1200 fpm. Bond strengths of film and nonwoven laminates are effectively controlled by air cooling devices which cause the air to flow substantially parallel to the extruded web during drawdown and provide a plurality of cooling air vortices to effectively cool the web. Film gauge control is also achieved by the method.

Methods of making plastic film and nonwoven laminates date back many years. For example, more than thirty years ago U.S. Pat. No. 3,484,835 (1968) issued to Trounstine, et al., and it is directed to embossed plastic film having desirable handling characteristics and fabricating useful articles such as diapers. Since that time, many patents have issued in the field. U.S. Pat. No. 5,202,173 issued on Apr. 13, 1993, for an ultra-soft thermoplastic film which was made by incrementally stretching the embossed film to achieve breathability. The film may include fillers. Polymer films of polycaprolactone (PCL) and starch polymer or polyvinyl alcohol (PVOH) upon incremental stretching also produce breathable products, as disclosed in U.S. Pat. Nos. 5,200,247 and 5,407,979. More recently, U.S. Pat. No. 5,865,926 issued for a method of making a cloth-like microporous laminate of a nonwoven fibrous web and thermoplastic film having air and moisture vapor permeabilities with liquid-barrier properties.
Methods of making microporous film products have also been known for some time. For example, U.S. Pat. No. 3,832,267, to Liu, teaches the melt-embossing of a polyolefin film containing a dispersed amorphous polymer phase prior to stretching or orientation to improve gas and moisture vapor transmission of the film. According to the Liu ""267 patent, a film of crystalline polypropylene having a dispersed amorphous polypropylene phase is first embossed prior to biaxially drawing (stretching) to produce an oriented imperforate film having greater permeability. The dispersed amorphous phase serves to provide microvoids to enhance the permeability of the otherwise imperforate film to improve moisture vapor transmission (MVT). The embossed film is preferably embossed and drawn sequentially.
In 1976, Schwarz published a paper which described polymer blends and compositions to produce microporous substrates (Eckhard C. A. Schwartz (Biax-Fiberfilm), xe2x80x9cNew Fibrillated Film Structures, Manufacture and Usesxe2x80x9d, Pap. Synth. Conf. (TAPPI), 1976, pages 33-39). According to this paper, a film of two or more incompatible polymers, where one polymer forms a continuous phase and a second polymer forms a discontinuous phase, upon being stretched will phase separate thereby leading to voids in the polymer matrix and increasing the porosity of the film. The continuous film matrix of a crystallizable polymer may also be filled with inorganic filler such as clay, titanium dioxide, calcium carbonate, etc., to provide microporosity in the stretched polymeric substrate.
Many other patents and publications disclose the phenomenon of making microporous thermoplastic film products. For example, European patent 141592 discloses the use of a polyolefin, particularly ethylene vinyl acetate (EVA) containing a dispersed polystyrene phase which, when stretched, produces a voided film which improves the moisture vapor permeability of the film. This EP ""592 patent also discloses the sequential steps of embossing the EVA film with thick and thin areas followed by stretching to first provide a film having voids which, when further stretched, produces a net-like product. U.S. Pat. Nos. 4,452,845 and 4,596,738 also disclose stretched thermoplastic films where the dispersed phase may be a polyethylene filled with calcium carbonate to provide the microvoids upon stretching. Later U.S. Pat. Nos. 4,777,073; 4,814,124; and 4,921,653 disclose the same processes described by the above-mentioned earlier publications involving the steps of first embossing a polyolefin film containing a filler and then stretching that film to provide a microporous product.
With reference to U.S. Pat. Nos. 4,705,812 and 4,705,813, microporous films have been produced from a blend of linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) with barium sulfate as the inorganic filler having an average particle diameter of 0.1-7 microns. It is also known to modify blends of LLDPE and LDPE with a thermoplastic rubber such as Kraton. Other patents, such as U.S. Pat. No. 4,582,871, disclose the use of thermoplastic styrene block tripolymers in the production of microporous films with other incompatible polymers such as styrene. There are other general teachings in the art such as the disclosures in U.S. Pat. Nos. 4,472,328 and 4,921,652.
Relevant patents regarding extrusion lamination of unstretched nonwoven webs include U.S. Pat. Nos. 2,714,571; 3,058,868; 4,522,203; 4,614,679; 4,692,368; 4,753,840 and 5,035,941. The above ""868 and ""368 patents disclose stretching extruded polymeric films prior to laminating with unstretched nonwoven fibrous webs at pressure roller nips. The ""203 and ""941 patents are directed to co-extruding multiple polymeric films with unstretched nonwoven webs at pressure roller nips. The ""840 patent discloses preforming nonwoven polymeric fiber materials prior to extrusion laminating with films to improve bonding between the nonwoven fibers and films. More specifically, the ""840 patent discloses conventional embossing techniques to form densified and undensified areas in nonwoven base plies prior to extrusion lamination to improve bonding between nonwoven fibrous webs and films by means of the densified fiber areas. The ""941 patent also teaches that unstretched nonwoven webs that are extrusion laminated to single ply polymeric films are susceptible to pinholes caused by fibers extending generally vertically from the plane of the fiber substrate and, accordingly, this patent discloses using multiple co-extruded film plies to prevent pinhole problems. Furthermore, methods for bonding loose nonwoven fibers to polymeric film are disclosed in U.S. Pat. Nos. 3,622,422; 4,379,197 and 4,725,473.
It has also been known to stretch nonwoven fibrous webs using intermeshing rollers to reduce basis weight and examples of patents in this area are U.S. Pat. Nos. 4,153,664 and 4,517,714. The ""664 patent discloses a method of incremental cross direction (CD) or machine direction (MD) stretching nonwoven fibrous webs using a pair of interdigitating rollers to strengthen and soften nonwoven webs. The ""664 patent also discloses an alternative embodiment wherein the nonwoven fibrous web is laminated to the thermoplastic film prior to intermesh stretching.
Efforts have also been made to make breathable non-woven composite barrier fabrics which are impervious to liquids, but which are permeable to water vapor. U.S. Pat. No. 5,409,761 is an example of a fabrication process from the patent art. According to this ""761 patent, a nonwoven composite fabric is made by ultrasonically bonding a microporous thermoplastic film to a layer of nonwoven fibrous thermoplastic material. These methods and other methods of making breathable laminates of nonwoven and thermoplastic materials tend to involve expensive manufacturing techniques and/or expensive raw materials.
Notwithstanding the extensive development of the art for making plastic films, breathable microporous films and laminates to provide air and moisture vapor permeabilities with liquid-barrier properties, further improvements are needed. In particular, improvements are desired for producing microporous film products and nonwoven laminates on high-speed production machinery without draw resonance. Also, in extrusion lamination of film and nonwoven webs, it has been difficult to achieve target bond levels at high speeds while maintaining the appearance of fabric and soft feel.
This invention is directed to a method of making plastic films, microporous thermoplastic films and laminates. The method is particularly advantages for operating on high-speed production machinery without draw resonance.
The method involves melting a thermoplastic composition and slot-die extruding a web of that composition through a cooling zone into a nip of rollers to form a film at a speed of at least about several hundred feet per minute (fpm). A stream of cooling gas (air) is directed at the web during its drawdown into a film. The air flow through the cooling zone is substantially parallel to the surface of the web to cool the web and form a film without draw resonance.
In the preferred form of the method, the effectiveness of the cooling gas is enhanced by creating a plurality of vortices of the gas as the stream moves through the zone to cool the web. The vortices enhance the effectiveness of the cooling gas by mixing the cooling gas and making the flow of the cooling gas turbulent in the cooling zone. A cooling device is used to create the vortices and make the gas stream move in different directions parallel to the movement of the web. Alternatively, the gas stream moves primarily in the same direction as the web movement or in a direction opposite to the movement of the web.
In the slot die extrusion lamination of the plastic web or film to a nonwoven fibrous web, a nonwoven fibrous web is introduced into the nip of rollers and the lamination temperature is controlled by the cooling gas to control target bond levels at high speeds of extrusion lamination. For example, target bond levels between the plastic film and the nonwoven web are achieved at speeds in excess of about 500 fpm even up to about 1200 fpm, or more. Target bond levels of, for example, 100 gms/cm between the film and nonwoven are achieved at line speeds on the order of 900 fpm for commercial purposes. The compressive force between the web and the film at the nip is controlled to bond the surface of the web to form a laminated sheet. Furthermore, even at high line speeds the film gauge is controlled without draw resonance. For example, a fixed film basis weight of about 40 grams per square meter (gsm) is achieved at 900 fpm. Thus, the method of cooling eliminates draw resonance which otherwise may normally be encountered under such conditions.
In another form of the invention, microporous thermoplastic films which are permeable to air and water vapor, but are a barrier to liquid, are produced. These breathable films or laminates of these films with nonwoven substrates are also produced at high speeds according to the method of this invention. In this form of the invention, a microporous formable thermoplastic composition is blended comprising a thermoplastic polymer and filler particles. Upon slot-die extrusion of such composition, followed by applying a stretching force to the film at high speeds along lines substantially and uniformly across the film and throughout its depth, a microporous film is formed. Breathable laminates are made when a nonwoven fibrous web is laminated to the film during the extrusion. The effectiveness of the cooling gas is enhanced by creating a plurality of vortices of the gas as the stream moves through the cooling zone to cool the web during extrusion lamination. Thereafter, preferably an incremental stretching force is applied to the film or the laminate at high speeds substantially and uniformly across the film and throughout its depth to provide a microporous film or laminate of film and nonwoven. Tentering may also be used to stretch the film or laminate.
Other benefits, advantages and objectives of this invention will be further understood with reference to the following detailed description.
It is a primary objective of this invention to produce plastic films, microporous films, and laminated products thereof with nonwoven fibrous webs, on high-speed production machinery. It is the further objective of the method to produce such films and laminated products of regular gauge without draw resonance. In the case of the microporous products, it is desired to produce breathable or microporous films and laminates with fibrous webs. It is another objective to produce such laminates having satisfactory bond strengths while maintaining the appearance of a fabric or cloth having suitable moisture vapor transmission rates and air permeability while maintaining liquid-barrier properties.
In a preferred mode, the high speed method of making a microporous thermoplastic film involves melt blending a composition comprising
(a) about 30% to about 45% by weight of a linear low density polyethylene (LLDPE),
(b) about 1% to about 10% by weight of a low density polyethylene (LDPE), and
(c) about 40% to about 60% by weight calcium carbonate filler particles of about 0.1 to 1 micron.
The melt-blended composition is slot-die extruded as a web through a cooling zone into a nip of rollers to form a film at speeds in the order of about 500 to about 1200 fpm without draw resonance. A device for directing a stream of cooling gas to flow in the cooling zone substantially parallel to the web surface is shown, for example, in U.S. Pat. Nos. 4,718,178 and 4,779,355. The entire disclosure of these patents is incorporated herein by reference as examples of devices which may be employed to provide enhanced effectiveness of the cooling gas by creating a plurality of vortices of the gas as the stream moves through the cooling zone to cool the web. Thereafter, an incremental stretching force is applied to the film at high speeds along lines substantially and uniformly across the film and throughout its depth to provide a microporous film.
The blend of LLDPE and LDPE within the above approximate ranges of components enables the production of microporous film at high speed when balanced with the prescribed amount of calcium carbonate. In particular, the LLDPE is present in an amount of about 30% to about 45% by weight in order to provide a sufficient amount of matrix to carry the calcium carbonate filler particles thereby enabling the film to be handled and stretched without pin holing and breakage. The LDPE in an amount of about 1% to about 10% by weight also contributes to the production of film without pin holing and enables the high speed production without draw resonance. The polymeric matrix is balanced with an amount of about 40% to about 60% by weight of calcium carbonate particles having an average particle diameter of preferably about 1 micron to achieve a sufficient moisture vapor transmission rate (MVTR) in the range of about 1000 gms/m2/day to 4000 gms/m2/day. Furthermore, the melt-blended composition may include a triblock polymer in an amount of about 0% to about 6% by weight to facilitate stretching in high-speed production without breakage. Other components such as about 5% by weight high density polyethylene (HDPE) and about 1% by weight antioxidants/processing aids are used. An incremental stretching force may be applied in line to the formed film under ambient conditions or at an elevated temperature at speeds of about several hundred fpm along lines substantially uniformly across the film and throughout it depth to provide a microporous film.
As stated above, the method of this invention also involves making film without draw resonance which is not microporous. In this manner, the above film compositions are extruded without the filler which is responsible for the microporosity. When either the film extrudate or microporous-formable extrudate is laminated to a nonwoven fibrous web during extrusion, the extrusion lamination is conducted at the same high speeds. For instance, a nonwoven fibrous web is introduced into the nip of rollers along with the microporous-formable thermoplastic extrudate at 500 to 1200 fpm. The compressive force between the fibrous web and the extrudate is controlled to bond one surface of the web to the film and form a laminate. The laminate is then incrementally stretched along lines substantially uniformly across the laminate and throughout its depth to render the film microporous. The laminate may be stretched in both the cross direction (CD) and the machine direction (MD) to provide breathable cloth-like liquid barriers capable of transmitting moisture vapor and air.
A. Materials for the Method
The thermoplastic polymer for the film preferably is of the polyolefin type and may be any of the class of thermoplastic polyolefin polymers or copolymers that are processable into a film or for direct lamination by melt extrusion onto the fibrous web. A number of thermoplastic copolymers suitable in the practice of the invention are of the normally-solid oxyalkanoyl polymers or dialkanoyl polymers represented by poly(caprolactone) blended with polyvinylalcohol or starch polymers that may be film-formed. The olefin based polymers include the most common ethylene or propylene based polymers such as polyethylene, polypropylene, and copolymers such as ethylene vinylacetate (EVA), ethylene methyl acrylate (EMA) and ethylene acrylic acid (EAA), or blends of such polyolefins. Other examples of polymers suitable for use as films include elastomeric polymers. Suitable elastomeric polymers may also be biodegradable or environmentally degradable. Suitable elastomeric polymers for the film include poly(ethylene-butene), poly(ethylene-hexene), poly(ethylene-octene), poly(ethylene-propylene), poly(styrene-butadiene-styrene), poly(styrene-isoprene-styrene), poly(styrene-ethylene-butylene-styrene), poly(ester-ether), poly(ether-amide), poly(ethylene-vinylacetate), poly(ethylene-methylacrylate), poly(ethylene-acrylic acid), poly(ethylene butylacrylate), polyurethane, poly(ethylene-propylene-diene), ethylene-propylene rubber. This new class of rubber-like polymers may also be employed and they are generally referred to herein as metallocene polymers or polyolefins produced from single-cite catalysts. The most preferred catalysts are known in the art as metallocene catalysts whereby ethylene, propylene, styrene and other olefins may be polymerized with butene, hexene, octene, etc., to provide elastomers suitable for use in accordance with the principles of this invention, such as poly(ethylene-butene), poly(ethylene-hexene), poly(ethylene-octene), poly(ethylene-propylene), and/or polyolefin terpolymers thereof.
The microporous-formable film composition can be achieved by formulating a thermoplastic polymer with suitable additives and pore-forming fillers to provide an extrudate or film for lamination with the nonwoven web. Calcium carbonate and barium sulfate particles are the most common fillers. Microporous-formable compositions of polyolefins, inorganic or organic pore-forming fillers and other additives to make microporous sheet materials are known. This method may be done in line and provides economies in manufacturing and/or materials over known methods of making laminates. In addition, as developed above, microporous-formable polymer compositions may be obtained from blends of polymers such as a blend of an alkanoyl polymer and polyvinyl alcohol as described in U.S. Pat. No. 5,200,247. In addition, blends of an alkanoyl polymer, destructured starch and an ethylene copolymer may be used as the microporous-formable polymer composition as described in U.S. Pat. No. 5,407,979. With these polymer blends, it is unnecessary to use pore-forming fillers to provide microporosity upon incremental stretching. Rather, the different polymer phases in the film themselves, when the film is stretched at ambient or room temperature, produce microvoids.
The nonwoven fibrous web may comprise fibers of polyethylene, polypropylene, polyesters, rayon, cellulose, nylon, and blends of such fibers. A number of definitions have been proposed for nonwoven fibrous webs. The fibers are usually staple fibers or continuous filaments. As used herein xe2x80x9cnonwoven fibrous webxe2x80x9d is used in its generic sense to define a generally planar structure that is relatively flat, flexible and porous, and is composed of staple fibers or continuous filaments. For a detailed description of nonwovens, see xe2x80x9cNonwoven Fabric Primer and Reference Samplerxe2x80x9d by E. A. Vaughn, Association of the Nonwoven Fabrics Industry, 3d Edition (1992).
In a preferred form, the microporous laminate employs a film having a gauge or a thickness between about 0.25 and 10 mils and, depending upon use, the film thickness will vary and, most preferably, in disposable applications is the order of about 0.25 to 2 mils in thickness. The nonwoven fibrous webs of the laminated sheet normally have a weight of about 5 grams per square yard to 75 grams per square yard preferably about 20 to about 40 grams per square yard. The composite or laminate can be incrementally stretched in the cross direction (CD) to form a CD stretched composite. Furthermore, CD stretching may be followed by or preceded by stretching in the machine direction (MD) to form a composite which is stretched in both CD and MD directions. As indicated above, the microporous films or laminates may be used in many different applications such as baby diapers, baby training pants, catamenial pads and garments, and the like where moisture vapor and air transmission properties, as well as fluid barrier properties, are needed.
B. Stretchers for the Microporous-Formable Laminates
A number of different stretchers and techniques may be employed to stretch the starting or original laminate of a nonwoven fibrous web and microporous-formable film. These laminates of nonwoven carded fibrous webs of staple fibers or nonwoven spun-bonded fibrous webs may be stretched with the stretchers and techniques described as follows:
1. Diagonal Intermeshing Stretcher
The diagonal intermeshing stretcher consists of a pair of left hand and right hand helical gear-like elements on parallel shafts. The shafts are disposed between two machine side plates, the lower shaft being located in fixed bearings and the upper shaft being located in bearings in vertically slidable members. The slidable members are adjustable in the vertical direction by wedge shaped elements operable by adjusting screws. Screwing the wedges out or in will move the vertically slidable member respectively down or up to further engage or disengage the gear-like teeth of the upper intermeshing roll with the lower intermeshing roll. Micrometers mounted to the side frames are operable to indicate the depth of engagement of the teeth of the intermeshing roll.
Air cylinders are employed to hold the slidable members in their lower engaged position firmly against the adjusting wedges to oppose the upward force exerted by the material being stretched. These cylinders may also be retracted to disengage the upper and lower intermeshing rolls from each other for purposes of threading material through the intermeshing equipment or in conjunction with a safety circuit which would open all the machine nip points when activated.
A drive means is typically utilized to drive the stationery intermeshing roll. If the upper intermeshing roll is to be disengageable for purposes of machine threading or safety, it is preferable to use an antibacklash gearing arrangement between the upper and lower intermeshing rolls to assure that upon reengagement the teeth of one intermeshing roll always fall between the teeth of the other intermeshing roll and potentially damaging physical contact between addenda of intermeshing teeth is avoided. If the intermeshing rolls are to remain in constant engagement, the upper intermeshing roll typically need not be driven. Drive may be accomplished by the driven intermeshing roll through the material being stretched.
The intermeshing rolls closely resemble fine pitch helical gears. In the preferred embodiment, the rolls have 5.935xe2x80x3 diameter, 45xc2x0 helix angle, a 0.100xe2x80x3 normal pitch, 30 diametral pitch, 14xc2xdxc2x0 pressure angle, and are basically a long addendum topped gear. This produces a narrow, deep tooth profile which allows up to about 0.090xe2x80x3 of intermeshing engagement and about 0.005xe2x80x3 clearance on the sides of the tooth for material thickness. The teeth are not designed to transmit rotational torque and do not contact metal-to-metal in normal intermeshing stretching operation.
2. Cross Direction Intermeshing Stretcher
The CD intermeshing stretching equipment is identical to the diagonal intermeshing stretcher with differences in the design of the intermeshing rolls and other minor areas noted below. Since the CD intermeshing elements are capable of large engagement depths, it is important that the equipment incorporate a means of causing the shafts of the two intermeshing rolls to remain parallel when the top shaft is raising or lowering. This is necessary to assure that the teeth of one intermeshing roll always fall between the teeth of the other intermeshing roll and potentially damaging physical contact between intermeshing teeth is avoided. This parallel motion is assured by a rack and gear arrangement wherein a stationary gear rack is attached to each side frame in juxtaposition to the vertically slidable members. A shaft traverses the side frames and operates in a bearing in each of the vertically slidable members. A gear resides on each end of this shaft and operates in engagement with the racks to produce the desired parallel motion.
The drive for the CD intermeshing stretcher must operate both upper and lower intermeshing rolls except in the case of intermeshing stretching of materials with a relatively high coefficient of friction. The drive need not be antibacklash, however, because a small amount of machine direction misalignment or drive slippage will cause no problem. The reason for this will become evident with a description of the CD intermeshing elements.
The CD intermeshing elements are machined from solid material but can best be described as an alternating stack of two different diameter disks. In the preferred embodiment, the intermeshing disks would be 6xe2x80x3 in diameter, 0.031xe2x80x3 thick, and have a full radius on their edge. The spacer disks separating the intermeshing disks would be 5xc2xdxe2x80x3 in diameter and 0.069xe2x80x3 in thickness. Two rolls of this configuration would be able to be intermeshed up to 0.231xe2x80x3 leaving 0.019xe2x80x3 clearance for material on all sides. As with the diagonal intermeshing stretcher, this CD intermeshing element configuration would have a 0.100xe2x80x3 pitch.
3. Machine Direction Intermeshing Stretcher
The MD intermeshing stretching equipment is identical to the diagonal intermeshing stretch except for the design of the intermeshing rolls. The MD intermeshing rolls closely resemble fine pitch spur gears. In the preferred embodiment, the rolls have a 5.933xe2x80x3 diameter, 0.100xe2x80x3 pitch, 30 Diametral pitch, 14xc2xdxc2x0 pressure angle, and are basically a long addendum, topped gear. A second pass was taken on these rolls with the gear hob offset 0.010xe2x80x3 to provide a narrowed tooth with more clearance. With about 0.090xe2x80x3 of engagement, this configuration will have about 0.010xe2x80x3 clearance on the sides for material thickness.
4. Incremental Stretching Technique
The above described diagonal, CD or MD intermeshing stretchers may be employed to produce the incrementally stretched laminate of nonwoven fibrous web and microporous-formable film to form the microporous laminate of this invention. The stretching operation is usually employed on an extrusion laminate of a nonwoven fibrous web of staple fibers or spun-bonded filaments and microporous-formable thermoplastic film. In one of the unique aspects of this invention a laminate of a nonwoven fibrous web of spun-bonded filaments may be incrementally stretched to provide a very soft fibrous finish to the laminate that looks like cloth. The laminate of nonwoven fibrous web and microporous-formable film is incrementally stretched using, for instance, the CD and/or MD intermeshing stretcher with one pass through the stretcher with a depth of roller engagement at about 0.025 inch to 0.120 inch at speeds from about 200 fpm to 500 fpm or faster. The results of such incremental or intermesh stretching produces laminates that have excellent breathability and liquid-barrier properties, yet provide superior bond strengths and soft cloth-like textures.
The following example illustrates the method of making films and laminates of this invention. In light of the example and this further detailed description, it is apparent to a person of ordinary skill in the art that variations thereof may be made without departing from the scope of this invention.

High speed method of making plastic film and nonwoven laminates


A snowboard tether for supporting a snowboard during a chair-lift ride and permitting the user to harness his or her back foot to the snowboard during the course of the chair-lift ride. A fastener attached to the snowboard allows the user to connect a strap to the fastener prior to sitting upon the chair-lift. The user may then attach the strap to the chair-lift, causing the strap to support the rear of the snowboard and permitting the user to exert downward force with his or her foot upon the rear binding of the snowboard. The fastener incorporates a storage container.

This invention relates to the sport of snowboarding. More specifically, the invention relates to a snowboard tether for supporting the snowboard during a chair-lift ride and permitting the user to harness his or her back foot to the snowboard during the course of the chair-lift ride.
Winter sports facilities are witnessing a dramatic increase in participation in the sport of snowboarding. A snowboard is a surfboard-like runner that includes a substantially flat board with a slippery bottom surface. Unlike a surfboard, on a snowboard the user attaches his or her feet to bindings that are affixed to the upper surface of the board.
Snowboards are typically used at winter sports facilities, like ski resorts, that have traditionally catered to skiers. The most prevalent mechanism for transporting the skiers or snowboarders to a high elevation at the resorts is a chair-lift. This mechanism, originally designed for skiers, typically involves a succession of bench seats suspended from a cable and pulley system that transports the benches from a bottom point to an elevated point and back again. At the bottom point, the skiers wait in turn to use the chair-lift mechanism. As each bench reaches the bottom point and turns around the pulley to advance up to the elevated point, the bench is positioned relatively close to the ground, enabling a skier to sit onto the bench. When the bench reaches the skiers, the skiers sit upon the bench, which is then whisked up to the elevated point by the cable and pulley system. At the elevated point, the mechanism is designed such that the skiers"" skis make contact with the ground and they can alight from the bench by standing up and pushing away.
To use the chair-lift, a snowboarder must detach his or her back foot in order to position himself or herself in front of an advancing bench. The bottom point of the chair-lift is typically a flat surface requiring manual force to propel oneself In some cases, the bottom point can involve icy portions or inclines upon which a snowboarder needs to maintain a fixed position, for instance, while positioned in front of an advancing bench. In these circumstances, the snowboarder also needs a foot in contact with the ground to prevent the snowboard from sliding out of position.
Accordingly, a snowboarder must mount the chair-lift with only the front foot attached to the bindings on the snowboard and with the back foot dangling free. Because snowboards can weigh a substantial amount, considerable downward force is experienced by the front leg of the snowboarder. This weight causes stress and fatigue that reduces the snowboarder""s endurance and ability to fully enjoy the sport.
Furthermore, at the elevated point of the chair-lift, the snowboarder must alight from the bench with only one foot attached to the snowboard. This necessitates the re-harnessing of the back foot to the binding before the snowboarder can resume snowboarding. This not only wastes time, but can cause congestion at the elevated point of the chair-lift as a number of snowboarders must stop their forward movement to re-harness their back feet. Congestion can lead to frustrations and collisions.
These problems could be alleviated by permitting a snowboarder to re-harness his or her back foot to the snowboard during the course of the chair-lift ride. Currently, a snowboarder is unable to re-harness his or her back foot because the center of gravity of the snowboard is between the front and back bindings on the snowboard. When the snowboarder""s front foot is the only attachment point, the weight of the snowboard exerts a torsional force on the front foot forcing the rear portion of the snowboard downwards. To harness the back foot, a snowboarder is required to apply substantial force through his or her back foot onto the rear binding of the snowboard. Without additional support for the rear portion of the snowboard, the snowboard cannot absorb that substantial force.
If the snowboarder were to attempt to provide the necessary support to the rear of the snowboard manually by grasping the rear portion with one hand, there exists a substantial danger that the snowboarder would fall forward off the chair lift. Almost all chair lifts incorporate a safety bar which can be manually rotated from a position directly in front of the snowboarders on the bench to a position above the snowboarders"" heads. When in front of the snowboarders, the safety bar prevents the snowboarders from accidentally falling forward off the chair during the ride. However, the safety bar also prevents the snowboarders from leaning forward to grasp the rear portion of their snowboards.
A number of leash or tether devices have been developed over the years in connection with snowboards for the purpose of securing the snowboard to the user in the event they become separated during a fall. These devices have typically involved a leash attached to the snowboard and around the front leg of the user. The front leg serves as the leashing point in these devices because the front leg remains in the binding, whereas the back leg must be released from time to time to permit propulsion over flat ground. These devices are designed for use while riding the snowboard, necessitating an arrangement of the leash secure to the user""s leg so as to prevent the leash cord from becoming entangled in tree branches or other protrusions during use of the snowboard.
These devices are inappropriate for use in supporting the snowboard to permit re-harnessing of the back foot because the leash or tether in these devices is attached at or near the front binding and does not prevent the torsional force exerted upon the front foot by the weight of the snowboard or the applied force of the back foot. Moreover, because the leash is intended for use while riding the snowboard, it must be tightly secured to the front leg of the snowboarder with a minimum of slack so as to prevent tangling or snagging of objects. Such an arrangement does not allow for translation of torsional forces through the leash to the chair-lift.
A number of these devices also involve an excessive number of components, rendering them expensive, cumbersome, unattractive and difficult to operate under winter conditions.
In order to permit a snowboarder to easily insert his or her back foot into the rear binding during a chair-lift ride, a device is needed that provides support for the rear portion of the snowboard such that the snowboarder is permitted to exert downward force upon the rear binding. Moreover, the device should provide support for the weight of the snowboard during the remainder of the chair-lift ride.
Such a device needs to be easily manipulated by a user wearing bulky handwear, such as thick mittens, and with a minimum of bending or effort. The device should be inexpensive and easy to assemble and attach to existing snowboards. The device needs to have a minimum number of parts, be easily operable and be easily carried when not in use. It also needs to be designed such that the snowboard retains its operating flexibility.
It would be advantageous if such a device could incorporate other useful functions. Space for mounting items on a snowboard is limited, so it is important to maximize the functions that can be incorporated into a single mounted piece. In particular, it would be useful if the device could also act as a carrying strap for the snowboard, as carrying a snowboard can be awkward and cumbersome. Carrying multiple snowboards is much easier if each snowboard has a carrying strap.
It would also be useful if the device could provide storage for items that a snowboarder would like to carry with him or her. When solid bulky items are carried in the snowboarder""s clothing, they can cause injury when the snowboarder falls upon them. Therefore, it would be advantageous if the mounting piece incorporated a storage element.
The prevent invention provides a snowboard tether that supports the rear of the snowboard during the course of a chair-lift ride so as to enable a snowboarder to re-harness his or her back to the snowboard and to provide support for the weight of the board during the ride. Additionally, it operates as a carrying strap and provides storage for personal belongings.
The present invention comprises a fastener affixed to the upper face of the rear portion of the snowboard and a strap. The strap comprises a length of material with manually releasable attachment devices affixed to either end. One of the manually releasable attachment devices is for connection to the fastener and the other manually releasable attachment device is for securing the strap to the chair lift. Through the strap, the chair-lift then supports the rear of the snowboard allowing the snowboarder to exert downward force upon the rear binding with his or her back foot.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.


A wheat variety designated 25R56, the plants and seeds of wheat variety 25R56, methods for producing a wheat plant produced by crossing the variety 25R56 with another wheat plant, and hybrid wheat seeds and plants produced by crossing the variety 25R56 with another wheat line or plant, and the creation of variants by mutagenesis or transformation of variety 25R56. This invention also relates to methods for producing other wheat varieties or breeding lines derived from wheat variety 25R56 and to wheat varieties or breeding lines produced by those methods.

Wheat is grown worldwide and is the most widely adapted cereal. There are five main wheat market classes. They include the four common wheat (Triticum aestivum L.) classes: matthiashard red winter, hard red spring, soft red winter, and white. The fifth class is durum (Triticum turgidum L.). Common wheats are used in a variety of food products such as bread, cookies, cakes, crackers, and noodles. In general the hard wheat classes are milled into flour used for breads and the soft wheat classes are milled into flour used for pastries and crackers. Wheat starch is used in the food and paper industries, as laundry starches, and in other products. Because of its use in baking, the grain quality of wheat is very important. To test the grain quality of wheat for use as flour, milling properties are analyzed. Important milling properties are relative hardness or softness, weight per bushel of wheat (test weight), siftability of the flour, break flour yield, middlings flour yield, total flour yield, flour ash content, and wheat-to-flour protein conversion. Good processing quality for flour is also important. Good quality characteristics for flour from soft wheats include low to medium-low protein content, a low water absorption, production of large-diameter test cookies and large volume cakes. Wheat glutenins and gliadins, which together confer the properties of elasticity and extensibility, play an important role in the grain quality. Changes in quality and quantity of these proteins change the end product for which the wheat can be used.
The present invention relates to a new and distinctive wheat variety, designated 25R56 which has been the result of years of careful breeding and selection as part of a wheat breeding program. There are numerous steps in the development of any novel, desirable plant germplasm. Plant breeding begins with the analysis and definition of problems and weaknesses of the current germplasm, the establishment of program goals, and the definition of specific breeding objectives. The next step is selection of germplasm that possess the traits to meet the program goals. The goal is to combine in a single variety an improved combination of desirable traits from the parental germplasm. These important traits may include higher seed yield, resistance to diseases and insects, tolerance to drought and heat, improved grain quality, and better agronomic qualities.
Field crops are bred through techniques that take advantage of the plant's method of pollination. A plant is self-pollinated if pollen from one flower is transferred to the same or another flower of the same plant. A plant is sib-pollinated when individuals within the same family or line are used for pollination. A plant is cross-pollinated if the pollen comes from a flower on a different plant from a different family or line. The term cross-pollination herein does not include self-pollination or sib-pollination. Wheat plants (Triticum aestivum L.), are recognized to be naturally self-pollinated plants which, while capable of undergoing cross-pollination, rarely do so in nature. Thus intervention for control of pollination is critical to the establishment of superior varieties.
A cross between two different homozygous lines produces a uniform population of hybrid plants that may be heterozygous for many gene loci. A cross of two heterozygous plants each that differ at a number of gene loci will produce a population of plants that differ genetically and will not be uniform. Regardless of parentage, plants that have been self-pollinated and selected for type for many generations become homozygous at almost all gene loci and produce a uniform population of true breeding progeny. The term "homozygous plant" is hereby defined as a plant with homozygous genes at 95% or more of its loci. The term "inbred" as used herein refers to a homozygous plant or a collection of homozygous plants.
Choice of breeding or selection methods depends on the mode of plant reproduction, the heritability of the trait(s) being improved, and the type of variety used commercially (e.g., F1 hybrid variety, pureline variety, etc.). For highly heritable traits, a choice of superior individual plants evaluated at a single location will be effective, whereas for traits with low heritability, selection should be based on mean values obtained from replicated evaluations of families of related plants. Popular selection methods commonly include pedigree selection, modified pedigree selection, mass selection, and recurrent selection.
The complexity of inheritance influences choice of the breeding method. In general breeding starts with the crossing of two genotypes (a "breeding cross"), each of which may have one or more desirable characteristics that is lacking in the other or which complements the other. If the two original parents do not provide all the desired characteristics, other sources can be included by making more crosses. In each successive filial generation, F1→F2; F2→F3; F3→F4; F4→F5, etc., plants are selfed to increase the homozygosity of the line. Typically in a breeding program five or more generations of selection and selfing are practiced to obtain a homozygous plant.
Pedigree breeding is commonly used for the improvement of self-pollinating crops. Two parents that possess favorable, complementary traits are crossed to produce an F1. An F2 population is produced by selfing or sibbing one or several F1's. Selection of the best individuals may begin in the F2 population; then, beginning in the F3, the best individuals in the best families are selected. Replicated testing of families can begin in the F4 generation to improve the effectiveness of selection for traits with low heritability. At an advanced stage of inbreeding (i.e., F5, F6 and F7), the best lines or mixtures of phenotypically similar lines are tested for potential release as new varieties.
Backcross breeding has been used to transfer genes for simply inherited, qualitative, traits from a donor parent into a desirable homozygous variety that is utilized as the recurrent parent. The source of the traits to be transferred is called the donor parent. After the initial cross, individuals possessing the desired trait or traits of the donor parent are selected and then repeatedly crossed (backcrossed) to the recurrent parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., variety) plus the desirable trait or traits transferred from the donor parent. This approach has been used extensively for breeding disease resistant varieties.
Each wheat breeding program should include a periodic, objective evaluation of the efficiency of the breeding procedure. Evaluation criteria vary depending on the goal and objectives, but should include gain from selection per year based on comparisons to an appropriate standard, overall value of the advanced breeding lines, and number of successful varieties produced per unit of input (e.g., per year, per dollar expended, etc.).
Various recurrent selection techniques are used to improve quantitatively inherited traits controlled by numerous genes. The use of recurrent selection in self-pollinating crops depends on the ease of pollination and the number of hybrid offspring from each successful cross. Recurrent selection can be used to improve populations of either self- or cross-pollinated crops. A genetically variable population of heterozygous individuals is either identified or created by intercrossing several different parents. The best plants are selected based on individual superiority, outstanding progeny, or excellent combining ability. The selected plants are intercrossed to produce a new population in which further cycles of selection are continued. Plants from the populations can be selected and selfed to create new varieties.
Another breeding method is single-seed descent. This procedure in the strict sense refers to planting a segregating population, harvesting a sample of one seed per plant, and using the one-seed sample to plant the next generation. When the population has been advanced from the F2 to the desired level of inbreeding, the plants from which lines are derived will each trace to different F2 individuals. The number of plants in a population declines each generation due to failure of some seeds to germinate or some plants to produce at least one seed. As a result, not all of the F2 plants originally sampled in the population will be represented by a progeny when generation advance is completed. In a multiple-seed procedure, wheat breeders commonly harvest one or more spikes (heads) from each plant in a population and thresh them together to form a bulk. Part of the bulk is used to plant the next generation and part is put in reserve. The procedure has been referred to as modified single-seed descent. The multiple-seed procedure has been used to save labor at harvest. It is considerably faster to thresh spikes with a machine than to remove one seed from each by hand for the single-seed procedure. The multiple-seed procedure also makes it possible to plant the same number of seeds of a population each generation of inbreeding. Enough seeds are harvested to make up for those plants that did not germinate or produce seed.
Bulk breeding can also be used. In the bulk breeding method an F2 population is grown. The seed from the populations is harvested in bulk and a sample of the seed is used to make a planting the next season. This cycle can be repeated several times. In general when individual plants are expected to have a high degree of homozygosity, individual plants are selected, tested, and increased for possible use as a variety.
Molecular markers including techniques such as Starch Gel Electrophoresis, Isozyme Electrophoresis, Restriction Fragment Length Polymorphisms (RFLPs), Randomly Amplified Polymorphic DNAs (RAPDs), Arbitrarily Primed Polymerase Chain Reaction (AP-PCR), DNA Amplification Fingerprinting (DAF), Sequence Characterized Amplified Regions (SCARs), Amplified Fragment Length Polymorphisms (AFLPs), Simple Sequence Repeats (SSRs), and Single Nucleotide Polymorphisms (SNPs) may be used in plant breeding methods. One use of molecular markers is Quantitative Trait Loci (QTL) mapping. QTL mapping is the use of markers, which are known to be closely linked to alleles that have measurable effects on a quantitative trait. Selection in the breeding process is based upon the accumulation of markers linked to the positive effecting alleles and/or the elimination of the markers linked to the negative effecting alleles from the plant's genome.
Molecular markers can also be used during the breeding process for the selection of qualitative traits. For example, markers closely linked to alleles or markers containing sequences within the actual alleles of interest can be used to select plants that contain the alleles of interest during a backcrossing breeding program. The markers can also be used to select for the genome of the recurrent parent and against the markers of the donor parent. Using this procedure can minimize the amount of genome from the donor parent that remains in the selected plants. It can also be used to reduce the number of crosses back to the recurrent parent needed in a backcrossing program (Openshaw et al. Marker-assisted Selection in Backcross Breeding. In: Proceedings Symposium of the Analysis of Molecular Marker Data, 5-6 Aug. 1994, pp. 41-43. Crop Science Society of America, Corvallis, Oreg.). The use of molecular markers in the selection process is often called Genetic Marker Enhanced Selection.
The production of double haploids can also be used for the development of homozygous lines in the breeding program. Double haploids are produced by the doubling of a set of chromosomes (1N) from a heterozygous plant to produce a completely homozygous individual. This can be advantageous because the process omits the generations of selfing needed to obtain a homozygous plant from a heterozygous source. Various methodologies of making double haploid plants in wheat have been developed (Laurie, D. A. and S. Reymondie, Plant Breeding, 1991, v. 106:182-189. Singh, N. et al., Cereal Research Communications, 2001, v. 29:289-296; Redha, A. et al., Plant Cell Tissue and Organ Culture, 2000, v. 63:167-172; U.S. Pat. No. 6,362,393).
Though pure-line varieties are the predominate form of wheat grown for commercial wheat production hybrid wheat is also used. Hybrid wheats are produced with the help of cytoplasmic male sterility, nuclear genetic male sterility, or chemicals. Various combinations of these three male sterility systems have been used in the production of hybrid wheat.
Descriptions of other breeding methods that are commonly used for different traits and crops can be found in one of several reference books (e.g., Allard, Principles of Plant Breeding, 1960; Simmonds, Principles of Crop Improvement, 1979; editor Heyne, Wheat and Wheat Improvement, 1987; Allan, "Wheat", Chapter 18, Principles of Crop Development, vol. 2, Fehr editor, 1987).
Promising advanced breeding lines are thoroughly tested and compared to appropriate standards in environments representative of the commercial target area(s). The best lines are candidates for new commercial varieties; those still deficient in a few traits may be used as parents to produce new populations for further selection.
A most difficult task is the identification of individuals that are genetically superior, because for most traits the true genotypic value is masked by other confounding plant traits or environmental factors. One method of identifying a superior genotype is to observe its performance relative to other experimental genotypes and to a widely grown standard variety. Generally a single observation is inconclusive, so replicated observations are required to provide a better estimate of its genetic worth.
A breeder uses various methods to help determine which plants should be selected from the segregating populations and ultimately which lines will be used for commercialization. In addition to the knowledge of the germplasm and other skills the breeder uses, a part of the selection process is dependent on experimental design coupled with the use of statistical analysis. Experimental design and statistical analysis are used to help determine which plants, which family of plants, and finally which lines are significantly better or different for one or more traits of interest. Experimental design methods are used to control error so that differences between two lines can be more accurately determined. Statistical analysis includes the calculation of mean values, determination of the statistical significance of the sources of variation, and the calculation of the appropriate variance components. Five and one percent significance levels are customarily used to determine whether a difference that occurs for a given trait is real or due to the environment or experimental error.
Plant breeding is the genetic manipulation of plants. The goal of wheat breeding is to develop new, unique and superior wheat varieties. In practical application of a wheat breeding program, the breeder initially selects and crosses two or more parental lines, followed by repeated selfing and selection, producing many new genetic combinations. The breeder can theoretically generate billions of different genetic combinations via crossing, selfing and mutations. The breeder has no direct control at the cellular level. Therefore, two breeders will never develop exactly the same line.
Each year, the plant breeder selects the germplasm to advance to the next generation. This germplasm is grown under unique and different geographical, climatic and soil conditions, and further selections are then made during and at the end of the growing season.
Proper testing should detect major faults and establish the level of superiority or improvement over current varieties. In addition to showing superior performance, there must be a demand for a new variety. The new variety must be compatible with industry standards, or must create a new market. The introduction of a new variety may incur additional costs to the seed producer, the grower, processor and consumer, for special advertising and marketing, altered seed and commercial production practices, and new product utilization. The testing preceding release of a new variety should take into consideration research and development costs as well as technical superiority of the final variety. It must also be feasible to produce seed easily and economically.
These processes, which lead to the final step of marketing and distribution, can take from six to twelve years from the time the first cross is made. Therefore, development of new varieties is a time-consuming process that requires precise forward planning, efficient use of resources, and a minimum of changes in direction.
Wheat (Triticum aestivum L.), is an important and valuable field crop. Thus, a continuing goal of wheat breeders is to develop stable, high yielding wheat varieties that are agronomically sound and have good grain quality for its intended use. To accomplish this goal, the wheat breeder must select and develop wheat plants that have the traits that result in superior varieties.